The Cycle Time Family

Cycle time often seems like a pretty simple concept.

Until one tries applying it in the real world.

Over the next few weeks and months, we'll explore, in detail, the math surrounding the various members of the cycle time family. Until then, the figure below may shed some light on the subject!

Got asked what would happen to inventory when the number of stocking locations change.  I thought for a minute and remembered a quick estimate.  The Square Root Law states that total safety stock can be approximated by multiplying the total inventory by the square root of the number of future warehouse locations divided by the current number.

X2 = (X1) * √ (n2/n1)

n1 = number of existing facilities
n2 = number of future facilities
X1 = existing inventory
X2 = future inventory

Here are two examples:


Benjamin Franklin said that, "Time is money."

We would be hard pressed to disagree.

Time is also a non-spatial continuum that is measured by change. But, that's another story. One that Dr. Mike, Physics Ph.D, can cover someday.

In any event, much of lean is about time and space. It's where we live and where we add value...or not.

Available Time

Available Time (Ta and Tar)

Available time (Ta), sometimes referred to as available working time or net available working time, is a fundamental lean concept. It would not be unreasonable to think this math entry would be very simple. However, there are more than a few important nuances.


The various categories that are listed on the sidebar and menu may be a bit obtuse. So, the following descriptions may be helpful.

Systems. It’s easy to get lost in lean tools and the related math. Lean practitioners remember that systems thinking is critical to maintaining the proper perspective and understanding. What kind of systems are we talking about? Well, stuff like Little’s Law, value stream analysis, process mapping, etc. These subjects, by their nature, reflect important inter-dependencies and with that…math.


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